1. Field of the Invention
The present invention relates to a control system and method for an automated transmission system, including a manually operated shift selector, for automatically controlling the changing or shifting of transmission gear ratios on a vehicle, while leaving the vehicle driver or operator some residual measure of control. In particular, the present invention relates to a control system and method for the semi-automatic control of a mechanical change gear transmission including means for automatically executing allowable driver-selected transmission ratio shifts. More particularly, the present invention relates to a system and method for controlling a semi-automatic mechanical transmission systems wherein movement to and retention of the shift selection lever or other selection device in the upshift or downshift direction or selection position for a first period of time is interpreted as an operator request for a single shift in that direction, and movement to and retention of the shift lever or other selection device in the upshift or downshift direction or selection position for at least a second, longer period of time, while the engine braking system is active, is interpreted as an operator request for a direct shift into a transmission ratio determined to provide optimum engine braking under current vehicle operating conditions.
2. Description of the Prior Art
Fully automatic transmission systems, for both heavy-duty vehicles (such as heavy-duty trucks and/or coaches) and for automobiles, that include sensors for sensing throttle openings or positions, vehicle speeds, engine speeds and the like, and automatically shift the vehicle transmission in accordance therewith, are well known in the prior art. Such fully automatic change-gear transmissions include transmissions wherein pressurized fluid is utilized to frictionally engage one or more members to other members or to a ground to achieve a selected gear ratio and automated mechanical transmissions utilizing electronic, hydraulic, mechanical and/or pneumatic logic and actuators to engage and disengage mechanical (i.e., positive) clutches to achieve a desired gear ratio. Examples of such transmissions may be seen by reference to U.S. Pat. No. 3,961,546; 4,081,065; 4,361,060; 5,050,079 and 5,109,729, the disclosures of which are incorporated herein by reference.
For many vehicles, vehicle operators like to control the selection of the gear ratios, particularly since they can see and/or know the nature of the road ahead and/or of the load being carried. This is accomplished by providing a semi-automatic mechanical transmission control wherein automatic changing between a plurality of gear ratios is provided, while normally permitting the driver to choose when to make a particular gear ratio change and whether to select the immediately consecutive ratio up or down or, by repetitive selection to skip one or more ratios. Examples of such a semi-automatic transmission control can be seen by reference to U.S. Pat. No. 4,648,290; 4,800,360; 4,930,081; 5,385,515 and 5,406,861, the disclosures of which are incorporated herein by reference.
While the above-described semi-automatic mechanical transmission control does provide a very desirable semi-automatic control, the control was subject to improvement. Selection of a direct single or skip shifts by repetitive pulses or movements of the shift selection lever is highly advantageous, however, the need to calculate the particular required ratio for a given set of operating conditions, the number of required movements, and of performing same, may be somewhat burdensome. This was particularly a concern in modern mechanical transmissions for heavy-duty vehicles which may have 9, 10, 12, 13, 16 or 18 forward speed ratios. Examples of such multi-speed mechanical transmissions may be seen by reference to U.S. Pat. Nos. 4,648,290; 4,735,109; 4,754,665 and 5,390,561, the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 5,385,515; 5,406,861 and 5,416,700, the disclosures of which are incorporated herein by reference, a control and control method responsive to retention of the shift selector in a given direction of displacement to cause the transmission to remain in the currently engaged ratio and a display to scroll in the given direction through the allowable engageable ratios and, upon release of the shift selection lever to the centered position, will perform a direct shift from the currently engaged ratio to the displayed ratio.
Systems wherein the operator could request a shift into a particular ratio to optimize a required performance by use of an additional selector are known. These systems are not totally satisfactory as an additional selector, additional connectors and the like are required.